scholarly journals Study of pulse structure and radiative mechanisms associations of long GRBs atz~1

2014 ◽  
Vol 10 (S313) ◽  
pp. 394-395
Author(s):  
Jonathan Quirola ◽  
Nicolás Vásquez
Keyword(s):  
Power Law ◽  
Gamma Ray ◽  
Band Model ◽  
Radiation Mechanisms ◽  
Spectral Parameters ◽  
Radiation Process ◽  
Spectral Models ◽  
Photon Index ◽  
Spectral Lag ◽  
Pulse Structure

AbstractIn this work, we have studied five different GRBs detected bySwift: GRB 071010B (z= 0.94), GRB 080411 (z= 1.03), GRB 080413B (z= 1.10), GRB 091208B (z= 1.06) and GRB 110715A (z= 0.82); Those GRBs, with similarzand have well defined pulses. To obtain spectral lag, we fit the light curves with a model having exponential rise and decay parts. In addition, we performed spectral analysis using three spectral models for different GRBs' regions:power law,cutoff power lawandband model. Additionaly, we releated spectral parameters such as photon index and luminosity with spectral lag. The analysis suggests that there are two types of pulses associated to specific radiation mechanisms which would reveal the radiation process of long gamma-ray bursts.

scholarly journals XMM-Newton spectrum of the magnetar CXOU J171405.7–381031

2019 ◽  
Vol 71 (4) ◽  
Author(s):  
Haruka Watanabe ◽  
Aya Bamba ◽  
Shinpei Shibata ◽  
Eri Watanabe
Keyword(s):  
Power Law ◽  
Time Variation ◽  
Supernova Remnant ◽  
Component Model ◽  
Time Variability ◽  
Spectral Parameters ◽  
X Ray ◽  
Two Component ◽  
Photon Index ◽  
Higher Temperature

Abstract We observe the magnetar CXOU J171405.7−381031 with XMM-Newton and obtain the most reliable X-ray spectral parameters for this magnetar. After removing the flux from the surrounding supernova remnant CTB 37B, the radiation of CXOU J171405.7−381031 is best described by a two-component model, consisting of a blackbody and power law. We obtain a blackbody temperature of $0.58^{+0.03}_{-0.03}$ keV, a photon index of $2.15^{+0.62}_{-0.68}$, and an unabsorbed 2–10 keV band flux of $2.33^{+0.02}_{-0.02} \times 10^{-12}$ erg cm−2 s−1. These new parameters enable us to compare CXOU J171405.7−381031 with other magnetars, and it is found that the luminosity, temperature, and photon index of CXOU J171405.7−381031 are aligned with the known trend among the magnetar population with a slightly higher temperature, which could be caused by its young age. All magnetars with a spin-down age of less than 1000 yr show time variation or bursts except for CXOU J171405.7−381031. We explore the time variability for six observations between 2006 and 2015, but there is no variation larger than ∼10%.

scholarly journals Rotationally driven VHE emission from the Vela pulsar

2019 ◽  
Vol 627 ◽  
pp. A22 ◽  
Author(s):  
Z. Osmanov ◽  
F. M. Rieger
Keyword(s):  
Particle Acceleration ◽  
Gamma Ray ◽  
Spectral Characteristics ◽  
High Energy ◽  
Radiation Mechanisms ◽  
Inverse Compton ◽  
Photon Index ◽  
Very High Energy ◽  
Vela Pulsar ◽  
Very High

Context. The recent detection of pulsed γ-ray emission from the Vela pulsar in the ∼10 to 100 GeV range by H.E.S.S. promises important potential to probe into the very high energy (VHE) radiation mechanisms of pulsars. Aims. A combined analysis of H.E.S.S. and Fermi-LAT data suggests that the leading wing of the P2 peak shows a new, hard gamma-ray component (with photon index as hard as Γ ∼ 3.5), setting in above 50 GeV and extending beyond 100 GeV. We study these findings in the context of rotationally driven (centrifugal) particle acceleration. Methods. We analyze achievable particle energies in the magnetosphere of the Vela pulsar and calculate the resultant emission properties. Results. Inverse Compton up-scattering of thermal photons from the surface of the star is shown to lead a pulsed VHE contribution reaching into the TeV regime with spectral characteristics compatible with current findings. If confirmed by further observations this could be the second case where rotationally driven processes turn out to be important to understand the VHE emission in young pulsars.

NUSTAR and Swift observations of AMXP Swift J1756.9−2508 during its 2018 outburst

2019 ◽  
Vol 489 (4) ◽  
pp. 5858-5865
Author(s):  
Binay Rai ◽  
Bikash Chandra Paul
Keyword(s):  
Spectral Analysis ◽  
Power Law ◽  
Power Law Model ◽  
Pulse Profile ◽  
Spectral Parameters ◽  
Time Resolved ◽  
Pulse Phase ◽  
Photon Index ◽  
Hard State ◽  
Orbital Phase

ABSTRACT We present here the timing and spectral analysis of the accreting millisecond pulsar (AMXP) SwiftJ1756.9−2508 during its recent outburst in 2018 using Swift and NUSTAR observations. The simultaneous fitting of the Swift and NUSTAR spectra indicates that the source was in the hard state with a cut-off energy of about 74.58 keV. We also study in detail the pulse profile of the AMXP and its dependence on energy. The colour–colour diagram of the source is different from those previously reported. We performed phase- and time-resolved spectral analysis using NUSTAR data. Pulse phase-resolved spectra were fitted with a power-law model and significant changes in the spectral parameters with pulse phase were observed. The orbital phase and time-resolved spectra were fitted with a cut-off power-law model. The column density and photon index obtained from orbital phase spectral analysis were found to show some anticorrelation with the flux. Through time-resolved spectral analysis, we observed that the spectral parameters show positive correlation with each other and with the flux. We do not observe a softening of the spectrum with time. No emission lines or Compton bump were observed in the spectrum of the AMXP.

SUZAKU VIEW OF POWERFUL GAMMA-RAY QUASARS

2008 ◽  
Vol 17 (09) ◽  
pp. 1483-1489
Author(s):  
JUN KATAOKA
Keyword(s):  
Power Law ◽  
Gamma Ray ◽  
Shock Acceleration ◽  
Soft Component ◽  
Diffusive Shock Acceleration ◽  
X Ray ◽  
Hard Power ◽  
Photon Index

We present the results from multiwavelength campaigns of three powerful gamma-ray quasars, PKS 1510-089, RBS 315 and Swift J0746.3+2548, recently organized with Suzaku. The Suzaku observation provided one of the highest S/N X-ray spectra ever reported between 0.3 and 50 keV. For these quasars, the X-ray spectrum is well represented by an extremely hard power-law with photon index Γ ≃ 1.2, but is augmented by an additional soft component apparently below 1 keV for PKS 1510-089, whereas a strong deficit of soft photons is observed in RBS 315. We model the broadband spectra of these powerful quasars and argue that the power of the jet is dominated by protons but with the number of electrons/positrons exceeding the number of protons by a factor ≃ 10. We also argue that an extremely hard X-ray spectra may result from a double power-law form of the injected electrons, with the break energy γ br ≃ 1000 corresponding to the anticipated threshold of diffusive shock acceleration.

scholarly journals X-ray Properties of 3C 111: Separation of Primary Nuclear Emission and Jet Continuum

Universe ◽  
2020 ◽  
Vol 6 (11) ◽  
pp. 219
Author(s):  
Elena Fedorova ◽  
B.I. Hnatyk ◽  
V.I. Zhdanov ◽  
A. Del Popolo
Keyword(s):  
Accretion Disk ◽  
Power Law ◽  
Line Emission ◽  
High Energy ◽  
Power Law Model ◽  
X Ray ◽  
Additional Information ◽  
Observational Dataset ◽  
Simple Power ◽  
Photon Index

3C111 is BLRG with signatures of both FSRQ and Sy1 in X-ray spectrum. The significant X-ray observational dataset was collected for it by INTEGRAL, XMM-Newton, SWIFT, Suzaku and others. The overall X-ray spectrum of 3C 111 shows signs of a peculiarity with the large value of the high-energy cut-off typical rather for RQ AGN, probably due to the jet contamination. Separating the jet counterpart in the X-ray spectrum of 3C 111 from the primary nuclear counterpart can answer the question is this nucleus truly peculiar or this is a fake “peculiarity” due to a significant jet contribution. In view of this question, our aim is to estimate separately the accretion disk/corona and non-thermal jet emission in the 3C 111 X-ray spectra within different observational periods. To separate the disk/corona and jet contributions in total continuum, we use the idea that radio and X-ray spectra of jet emission can be described by a simple power-law model with the same photon index. This additional information allows us to derive rather accurate values of these contributions. In order to test these results, we also consider relations between the nuclear continuum and the line emission.

scholarly journals Magnetar X-ray emission mechanisms

2012 ◽  
Vol 8 (S291) ◽  
pp. 160-160
Author(s):  
Silvia Zane
Keyword(s):  
Spectral Analysis ◽  
Physical Interpretation ◽  
Spectral Properties ◽  
Gamma Ray ◽  
X Ray ◽  
Spectral Components ◽  
Self Consistent ◽  
Photon Index ◽  
Index 2 ◽  
Surface Fields

AbstractSoft gamma-ray repeaters (SGRs) and anomalous X-ray pulsars (AXPs) are peculiar X-ray sources which are believed to be magnetars: ultra-magnetized neutron stars which emission is dominated by surface fields (often in excess of 1E14 G, i.e. well above the QED threshold).Spectral analysis is an important tool in magnetar astrophysics since it can provide key information on the emission mechanisms. The first attempts at modelling the persistent (i.e. outside bursts) soft X-ray (¡10 keV) spectra of AXPs proved that a model consisting of a blackbody (kT 0.3-0.6 keV) plus a power-law (photon index 2-4) could successfully reproduce the observed emission. Moreover, INTEGRAL observations have shown that, while in quiescence, magnetars emit substantial persistent radiation also at higher energies, up to a few hundreds of keV. However, a convincing physical interpretation of the various spectral components is still missing.In this talk I will focus on the interpretation of magnetar spectral properties during quiescence. I will summarise the present status of the art and the currents attempts to model the broadband persistent emission of magnetars (from IR to hard Xrays) within a self consistent, physical scenario.

scholarly journals Detection of the Geminga pulsar with MAGIC hints at a power-law tail emission beyond 15 GeV

2020 ◽  
Vol 643 ◽  
pp. L14
Author(s):  
◽  
V. A. Acciari ◽  
S. Ansoldi ◽  
L. A. Antonelli ◽  
A. Arbet Engels ◽  
...  
Keyword(s):  
Energy Range ◽  
Power Law ◽  
Gamma Ray ◽  
Low Energy ◽  
Significance Level ◽  
Inverse Compton Scattering ◽  
Curvature Radiation ◽  
Sensitivity Range ◽  
Inverse Compton ◽  
First Time

We report the detection of pulsed gamma-ray emission from the Geminga pulsar (PSR J0633+1746) between 15 GeV and 75 GeV. This is the first time a middle-aged pulsar has been detected up to these energies. Observations were carried out with the MAGIC telescopes between 2017 and 2019 using the low-energy threshold Sum-Trigger-II system. After quality selection cuts, ∼80 h of observational data were used for this analysis. To compare with the emission at lower energies below the sensitivity range of MAGIC, 11 years of Fermi-LAT data above 100 MeV were also analysed. From the two pulses per rotation seen by Fermi-LAT, only the second one, P2, is detected in the MAGIC energy range, with a significance of 6.3σ. The spectrum measured by MAGIC is well-represented by a simple power law of spectral index Γ = 5.62 ± 0.54, which smoothly extends the Fermi-LAT spectrum. A joint fit to MAGIC and Fermi-LAT data rules out the existence of a sub-exponential cut-off in the combined energy range at the 3.6σ significance level. The power-law tail emission detected by MAGIC is interpreted as the transition from curvature radiation to Inverse Compton Scattering of particles accelerated in the northern outer gap.

scholarly journals Broad-band study of high-synchrotron-peaked BL Lac object 1ES 1218+304

2020 ◽  
Vol 496 (4) ◽  
pp. 5518-5527
Author(s):  
N Sahakyan
Keyword(s):  
Energy Distribution ◽  
Electron Energy ◽  
Power Law ◽  
Spectral Energy Distribution ◽  
Broad Band ◽  
Energy Distributions ◽  
X Ray ◽  
Bl Lac ◽  
Photon Index ◽  
Γ Ray

ABSTRACT The origin of the multiwavelength emission from the high-synchrotron-peaked BL Lac 1ES 1218+304 is studied using the data from SwiftUVOT/XRT, NuSTAR, and Fermi-LAT. A detailed temporal and spectral analysis of the data observed during 2008–2020 in the  γ-ray (>100 MeV), X-ray (0.3–70 keV), and optical/UV bands is performed. The γ-ray spectrum is hard with a photon index of 1.71 ± 0.02 above 100 MeV. The SwiftUVOT/XRT data show a flux increase in the UV/optical and X-ray bands; the highest 0.3–3 keV X-ray flux was (1.13 ± 0.02) × 10−10 erg cm−2 s−1. In the 0.3–10 keV range, the averaged X-ray photon index is >2.0 which softens to 2.56 ± 0.028 in the 3–50 keV band. However, in some periods, the X-ray photon index became extremely hard (<1.8), indicating that the peak of the synchrotron component was above 1 keV, and so 1ES 1218+304 behaved like an extreme synchrotron BL Lac. The hardest X-ray photon index of 1ES 1218+304 was 1.60 ± 0.05 on MJD 58489. The time-averaged multiwavelength spectral energy distribution is modelled within a one-zone synchrotron self-Compton leptonic model using a broken power law and power law with an exponential cutoff electron energy distributions. The data are well explained when the electron energy distribution is $E_{\rm e}^{-2.1}$ extending up to γbr/cut ≃ (1.7 − 4.3) × 105, and the magnetic field is weak (B ∼ 1.5 × 10−2 G). By solving the kinetic equation for electron evolution in the emitting region, the obtained electron energy distributions are discussed considering particle injection, cooling, and escape.

scholarly journals Prolonged sub-luminous state of the new transitional pulsar candidate CXOU J110926.4−650224

2019 ◽  
Vol 622 ◽  
pp. A211 ◽  
Author(s):  
Francesco Coti Zelati ◽  
Alessandro Papitto ◽  
Domitilla de Martino ◽  
David A. H. Buckley ◽  
Alida Odendaal ◽  
...  
Keyword(s):  
Gamma Ray ◽  
Broad Band ◽  
Optical Emission ◽  
Bimodal Distribution ◽  
X Ray ◽  
The Past ◽  
Upper Limits ◽  
Photon Index ◽  
Multi Wavelength ◽  
Absorbed Power

We report on a multi-wavelength study of the unclassified X-ray source CXOU J110926.4−650224 (J1109). We identified the optical counterpart as a blue star with a magnitude of ∼20.1 (3300–10500 Å). The optical emission was variable on timescales from hundreds to thousands of seconds. The spectrum showed prominent emission lines with variable profiles at different epochs. Simultaneous XMM-Newton and NuSTAR observations revealed a bimodal distribution of the X-ray count rates on timescales as short as tens of seconds, as well as sporadic flaring activity. The average broad-band (0.3–79 keV) spectrum was adequately described by an absorbed power law model with photon index of Γ = 1.63  ±  0.01 (at 1σ c.l.), and the X-ray luminosity was (2.16  ±  0.04)  ×  1034 erg s−1 for a distance of 4 kpc. Based on observations with different instruments, the X-ray luminosity has remained relatively steady over the past ∼15 years. J1109 is spatially associated with the gamma-ray source FL8Y J1109.8−6500, which was detected with Fermi at an average luminosity of (1.5  ±  0.2)  ×  1034 erg s−1 (assuming the distance of J1109) over the 0.1–300 GeV energy band between 2008 and 2016. The source was undetected during ATCA radio observations that were simultaneous with NuSTAR, down to a 3σ flux upper limit of 18 μJy beam−1 (at 7.25 GHz). We show that the phenomenological properties of J1109 point to a binary transitional pulsar candidate currently in a sub-luminous accretion disk state, and that the upper limits derived for the radio emission are consistent with the expected radio luminosity for accreting neutron stars at similar X-ray luminosities.

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